Supercooling means a phenomenon where a molten object or a solid cooled to below a phase transition temperature in a balanced state is not changed. A material has stable states by temperatures. If a temperature is slowly changed, elements composing the material keep pace with the temperature variations, maintaining stable states at each temperature. However, if the temperature is sharply changed, the elements can not enter stable states at each temperature. Therefore, the elements maintain a stable state of a start point temperature, or some of the elements fail to enter a state of a final point temperature.
For example, when water is slowly cooled, it is not frozen temporarily below 0° C. However, when an object enters a supercooled state, it has a kind of quasi-stable state. Since such an unstable balanced state is easily broken by slight stimulation, the object tends to be transited into a more stable state. That is, if a small piece of material is put into the supercooled liquid, or if the liquid is suddenly shaken, the liquid is frozen at once, so that a temperature of the liquid reaches a freezing point. The liquid maintains a stable balanced state at the temperature.
In general, foods such as vegetables, fruits, meats and beverages are refrigerated or frozen to be kept fresh. Such foods contain a liquid element such as water. If the liquid element is cooled below a phase transition temperature, it is transited into a solid element at a specific point.
A stored object such as water can be maintained in a supercooled state for a short time. However, in case moisture of food is frozen, the food needs to be maintained in the supercooled state for an extended period of time so as to keep quality and extend a storage period.
The supercooling continuation technology has been applied to an electrostatic field processing method, an electrostatic field processing apparatus, and electrodes therefor in Korean Laid-Open Patent 2000-0011081.
In the conventional art, an electric or magnetic field is applied to a stored cooled object so that the object can enter a supercooled state. A complicate apparatus for generating the electric or magnetic field is required to maintain the stored object in the supercooled state. In addition, power consumption considerably increases in the generation of the electric or magnetic field.
Moreover, the apparatus for generating the electric or magnetic field further needs a user safety device (e.g., an electric or magnetic field shielding structure, a cutoff device, etc.) in the generation or cutoff of the electric field or magnetic field due to high power.